Implementation of a programmable electromechanical chopper with adjustable frequency and duty cycle for specific heat measurements

A hard disk mechanism was used as an electromechanical light chopper controlled by software developed in LabVIEW with an accuracy of ±0.01 Hz in frequency to realize specific heat measurements. This chopper can be used in applications in experimental techniques in which low-frequency light excitation is required. The software provides an user interface to set the excitation frequency and its duty cycle. The evaluation of the efficiency was measured by installing the device in a fully automated high-resolution AC calorimetry system. The device provides a light cutter signal with a frequency varying from 1 mHz to 40 Hz. Employing the desired wave function, the excitation mode provided by this design can be used under theoretical models proposed for the specific heat technique, obtaining an increased efficiency in the measurements of the specific heat response for the studied materials. This paper reports the performance characteristics of the technology of an asymmetric CA-chopper, which can optimize efficiency in capturing the measurement of the response of specific heat of any given study material in a high-resolution ac calorimetry system. The chopper consists entirely of the positioning mechanism of a hard disk.